Pads and sweeps made from polypropylene melt blown fabrics are commonly used by first responders to absorb spilled oil. These fabrics have little strength and tend to fall apart after absorbing oil when deployed in the field. One example of a melt blown fabric used for this purpose has a basis weight of about 5.49 ounces per square yard (osy) as measured by American Society for Testing and Materials test method (ASTM) D3776, a grab breaking strength in the machine direction of about 8.1 pounds force (lbf) as measured by ASTM D5034, a grab elongation in the machine direction of about 9% as measured by ASTM D5034, a grab breaking strength in the cross direction of about 9.5 lbf as measured by ASTM D5034, a grab elongation in the cross direction of about 43.3% as measured by ASTM D5034, a burst strength of about 15.8 lb/in2 as measured by ASTM D3786, a thickness of about 0.078 mils as measured by ASTM D1777, and an air permeability of about 53.4 cubic feet per minute per square foot (ft3/min/ft2) as measured by ASTM D737.
Polypropylene is often used since it is available at a relatively low cost. The fabrics are commonly made into items such as pads and sweeps. Sweeps are fabrics with a seamed edge and a rope or band attached to at least one edge. The sweeps are then passed on the surface of the water to capture and remove spilled crude oil from the environment. These items lose integrity when deployed and exposed to oil, making it difficult to gather and collect them after they have absorbed oil. They also will easily break or disintegrate since they have such low strength when pulled or dragged in the field, creating difficulties when crews are cleaning up oil spills. When using polypropylene fabrics to fabricate sweeps, a band is typically added to one or more longitudinal edges and vertical edges to give the sweep more strength for pulling or dragging and to prevent disintegration when the sweep becomes wet with oil. This adds cost and adds at least one additional fabrication step. In addition, items made from these polypropylene fabrics do not remove oil sheen on the surface of water. A 100 foot roll of sweep made using this fabric has a diameter of about 16 to 17 inches when rolled up.
A typical remediation plan to address an oil spill involves the deployment of booms to contain the spilled oil and pads to absorb the spilled oil or mechanical means such as skimmers or vacuum pump trucks to collect the spilled oil. Often, mops, pom poms, or snares made from split film polyethylene material are used to collect the spilled crude oil. The polyethylene split film material is not effective in absorbing lower viscosity fluids and performs best on very thick material such as weathered crude oil in the viscosity range of about 150,000 centistokes or higher. For a common comparison, this viscosity is similar to tomato paste or peanut butter. Crude oil has a viscosity of about 1 to 5 centistokes. Commercially available snares are made by tying 30 pom poms on 50 feet of rope. These pom poms weigh about 1 pound each. First responders will deploy these snares early during a spill to no avail in removing crude oil from the environment. A pom pom made from this slit film polyethylene material absorbs about 1.87 times its own dry weight of crude oil.
Sweeps are also used to absorb oil and frequently used in an unsuccessful attempt to remove oil sheen. Sweeps are made from polypropylene fabrics similar to the fabric used for absorbent pads. They are commercially available in 100 foot rolls that are about 19 inches wide. Since the polypropylene material is so thick, the 100 foot roll of sweep tends to be bulky and hard to handle.
In addition, spills of liquids happen in industry and in the transporting of chemicals. Several methods are currently used to remove spilled materials from the environment including the use of absorbent pads and other absorbent articles. Accidental spills of petroleum products can have profound, far reaching environmental effects, especially if the spilled material is dispersed in water as an oil in water emulsion. First responders to spills of oil or other liquids in the environment will initially try to contain the oil then remove it from the environment. Removal methods include but are not limited to skimming liquids off the surfaces of water, absorbing the liquids on pads, snares, mops and other absorbent articles and pressure washing surfaces then collecting the runoff for disposal. Examples of absorbent pads are described in many patents. For example, pads made from melt blown polypropylene or spunbond polypropylene or both are well known in the art.
Several commercially available absorbent pads and articles currently used are made of melt blown fabrics. While these fabrics absorb several times their dry weight in oil they tend to not maintain their integrity after they have been deployed and have absorbed liquids. They are typically in the basis weight range of about 6 to 10 ounces per square yard (osy) and do not have near the strength per basis weight of spunbond fabrics after they have become wet with oil. They tend to be heavy and dense.
The process of extruding and forming thin fibers of polypropylene and other thermoplastics, generally called “melt blowing” is well known and described in U.S. Pat. No. 3,978,185 to Buntin et al. and U.S. Pat. No. 4,100,324 to Anderson et al. Multiple plies of melt blown sheets and combinations of melt blown sheets and spunbond polypropylene sheets combined by ultrasonically welding the plies together at a number of points uniformly across the length and width are also commercially available. These sheets are then processed into rolls, pads, and wipes for uses such as cleaning an oil spill on a factory floor, wiping off oily machinery, skimming oil off of the surface of a body of water, and for a variety of other applications where the user desires to collect hydrocarbons or other liquids. These pads require some method of bonding to increase the strength and integrity or else the melt blown fibers disassociate when pulled or when the pad becomes soiled with oil. U.S. Pat. No. 4,041,203 to Brock discloses a nonwoven material in the form of a laminate having an integrated mat of generally discontinuous thermoplastic fibers as a layer and a web of substantially continuous and randomly deposited filaments of a thermoplastic polymer as another layer. The mat and web are attached at intermittent discrete bond regions by passing the material through a calendaring system. Similarly, when a layer of melt blown fabric is sandwiched between two spunbond layers this is commonly referred to as a spunbond-melt blown-spunbond fabric or SMS fabric. Pads are also made from these fabrics.
U.S. Pat. No. 5,391,415 describes an absorbing article with twelve to twenty-four ounces per square yards (osy) of balls of fluff formed from out-of-planed crimped fibers with an outer porous fabric in the range of 3-5.1 osy that is combined with lanes that are no more than 0.4 cm wide forming 1-4 cm channels between successive lanes. This article will absorb at least about 6 times its dry weight of A-520 hydraulic oil. Narrow channels as described in this patent require a large amount of stitching and also reduce the thickness and increase the density around the stitched area. This reduces the amount of oil that can be absorbed by the mass near and in the stitching. An article with the minimum number of seams required to provide the strength to prevent ripping or tearing and to provide integrity when wet with oil or water or both provides an advantage by increasing the oil absorbing capability of the material and minimizing the cost to make the article because less sewing thread is used. It is also an advantage to have an article with a low basis weight and the ability to absorb many times its dry weight in oil.
Other materials such as cellulose are often used to make absorbent articles. None of the materials or articles in the prior art are effective in removing oil sheen.
Hay bales are used to prevent soil erosion, control water flow, and sediment flow on road sides, in culverts and ditches, on construction locations and other sites. Hay bales have several disadvantages including but not limited to biodegradability and supply issues due to climate conditions such as drought and consistency of quality. U.S. Pat. No. 6,422,787 to Mikell discloses a synthetic bale made from ground carpet fibers that have been needle punched into a mat and rolled into a bale. This bale is then covered with netting made from a mesh material. Carpet fibers made using this technique are released in the environment when the synthetic bale is deployed.